North Pines will close for the year on November 2nd and Lower Pines will close Oct 26th. (reservations required and some sites are available). Upper pines (open year round) goes off the reservation system on December 1st. So to answer your question....Anytime after December 1st.

If you can avoid weekends, probably any time now. I nearly always see "space available" signs at the kiosk even when it was originally sold out, and there are always empty campsites, especially if the weather turns cold, rainy, etc. Not so much if the weather's great, but still possible.

No guarantees, of course, and I always make reservations ahead of time, but this time of year there are lots of cancellations, and at worst you might have to move your site if you're staying a while. There are spaces available now toward the end of October, off-weekend for several nights.

i only live 2 & 1/2 hrs away, so i was hoping to run up there this Saturday to camp one night. i guess i'd really be chancing it if i did... worst thing that could happen is, i have to turn around and come home the same day (which i've done many times before)... i'll go up for the day and come home at night.